Effect of Diet Containing Inclusion of Phenolic Monoterpenes Carvacrol, Menthol and Thymol on Cellular and Humoral Immune Response in Broilers

     This study was conducted to evaluate the effects of diet containing inclusion of carvacrol, menthol and thymol at 400, 200 and 200 mg/kg, respectively, on performance, cell-mediated and humoral immune response using 96 broiler chicks in a completely randomized block design in 12 replicates of 2 birds each. Feed intake reduced in birds received diet containing menthol during days 14 to 42 of age (P<0.05). No changes in weight gain and feed conversion ratio were observed in birds fed with supplemented diets compared with control birds (P>0.05). Mean antibody titer against infectious Bursal and Newcastle viruses was not differ for the chicks received diets supplemented with carvacrol, menthol and thymol at day 42 of age (P>0.05). Proportional weight of immune organs including the bursa of fabricius, spleen and thymus was not affected by the addition of monoterpens in diet at day 42 of age (P>0.05). The percentage of heterophils in blood was lower in birds grown on menthol-added diets than in control chicks (P<0.05). The experimental diets reduced the inflammation induced by phytohemagglutinin (PHA) injection at 6, 12, 24 and 48 hours after injection during days 32 to 35 of age (P <0.05). Based on dermal inflammation caused by PHA injection, carvacrol, menthol and thymol did not stimulate cellular immunity but showed significant anti-inflammatory activity.